Karyology of four Indian snakes

Cytogenetic studies were carried out on four species of Indian snakes viz Eryx conicus (Family Boidae), Naja naja naja (Family Elapidae), Vipera russelli and Echis carinatus (Family Viperidae) collected from Jammu region (J&K). Both E. conicus and N. n. naja show deviation from typical ophidian karyotype (2n=36), having 2n=34 (16 macroand 18 microchromosomes, NF=42) in E. conicus and 2n=38 (16 macroand 22 microchromosomes and NF=50) in N. n. naja. In both the species sex chromosomes are undifferentiated. V. russelli and E. carinatus exhibited typical ophidian karyotype viz 2n=36 (16 macroand 20 microchromosomes) with NF=48 and 50 respectively. They possess a well differentiated ‘ZW’ sex mechanism in female, where ‘W’ is smaller and submetacentric, a final step in the evolution of sex chromosome in snakes and ‘Z’ is larger and metacentric.